The present invention is related to the field of clamping tools, and more particularly, to clamping tools that clamp overlapping work pieces to facilitate drilling of the work pieces.
Accurate hole location is critical to the attachment of the parts of an assembly during a manufacturing process. For this reason, overlapping parts are typically drilled while assembled to ensure matching hole configuration. However, burrs tend to develop around the drill holes that interfere with the mating of the parts. These burrs are inaccessibly trapped in the interstices of the overlapping parts while the parts are assembled. Therefore, assembly of the overlapping parts typically requires pre-assembly of the parts, drilling of the holes into the parts, disassembly of the parts, deburring of the drilled holes, the application of sealant between the parts and reassembly of the parts into a final configuration. Assembly, disassembly and reassembly are time consuming processes that slow production.
The formation of burrs can be reduced, or avoided, if sufficient pressure is applied to hold the parts together during drilling. Manual techniques for applying pressure to a parts assembly include the use of conventional clamps, such as C-clamps, and temporary fasteners, such as wedge locks. Despite obviating the need to disassemble and reassemble the parts for deburring, manual clamp deployment still requires significant time and effort on the part of the worker. U.S. Pat. No. 4,770,401 to Donaldson discloses a powered C-clamp that includes an axial clamp member 86 that is movable by a gear 74 which is driven by an electrical drive assembly 16. The powered C-clamp advantageously reduces worker fatigue associated with tightening manual clamps. The aforementioned clamps, however, often do not produce repeatable clamping forces, are prone to excessive tightening which results in damage of the parts, and/or succeed only in producing sufficient clamping forces in a localized area about the clamp jaws. Localized force application limits hole drilling to relatively small areas on the parts in proximity to the clamp.
Therefore, it would be advantageous to have a powered clamp for clamping together parts with sufficient force to eliminate the formation of burrs between parts during drilling. It would be further advantageous to have a powered clamp that eliminates the manual effort associated with clamping the parts. It would also be advantageous to have a clamp that was not prone to excessive tightening and that produced sufficient clamping forces over a relatively wide area.
The present invention addresses the above needs and achieves other advantages by providing an improved pressure clamp assembly for clamping a plurality of overlapping members together. The pressure clamp includes a pair of compression members attached to a clamp body and driven together by a power source. The power source preferably includes a fluid pressure cylinder that repeatably produces high clamping forces so as to inhibit the production of inter-laminate burrs during drilling. The compression members preferably each include an elongated compression foot that distributes the clamping pressure over a wide area to allow drilling in a relatively wide range of locations. In addition, each compression foot defines a drill bit assembly guide that facilitates accurate hole drilling.
In one embodiment, the present invention includes a pressure clamp assembly for clamping a plurality of overlapping members together and for facilitating accurate drilling of the overlapping members using a drill and a drill bit assembly while minimizing the production of burrs. The pressure clamp assembly includes a clamp body, a first and second compression members and a power source. The compression members are attached to the clamp body. The first compression member is opposingly spaced from the second compression member so as to define a gap. At least one of the compression members is movable toward the other one of the compression members. The first compression member defines a drill bit assembly guide that is configured to receive and guide the drill bit assembly of the drill. The power source is operable to drive the at least one movable compression member so as to shrink the gap and clampingly engage the plurality of overlapping members between the compression members with sufficient pressure to reduce inter-laminate burring during operation of the drill.
In another aspect, the clamp body has a U-shape including a pair of free ends. The first compression member is attached to a first one of the free ends, and the second compression member is attached to a second one of the free ends.
In another aspect, the power source includes a pressure cylinder connected to a fluid pressure supply. The second compression member is attached to a free end of a piston shaft of the pressure cylinder, and is moveable thereby in the direction of the first compression member.
In another embodiment, the power source further includes a pair of second pressure cylinders connected to the pressure supply. The first compression member is connected to a free end of a piston shaft of each of the second pressure cylinders and is moveable thereby in the direction of the second compression member. The pair of second pressure cylinders are preferably spaced across the first compression member. In this configuration, the first one of the free ends of the clamp body defines a drill opening between the pair of second pressure cylinders. The drill opening is configured to allow access of the drill and drill bit assembly through the first one of the free ends to the drill assembly guide.
In another embodiment, the first compression member has an elongated foot shape and the first compression member further defines a second drill bit assembly guide. Preferably, the first and second drill bit assembly guides are spaced across the elongated foot.
In yet another embodiment, the pressure clamp includes a swing mount assembly that connects the second compression member to the body. The swing mount allows the second compression member to swing with respect to the body, and the first compression member. Preferably, the first compression member is an elongated compression foot defining the drill bit assembly guide and the second compression member is a second elongated compression foot defining a second drill bit assembly guide.
In another aspect, the power source includes a pressure cylinder connected to a fluid pressure supply and a linkage attaching a rod of the pressure cylinder to the second compression member to rotate the second compression member about the swing-mount. Preferably, the linkage includes a lever arm rotatably attached at a first end to the rod of the cylinder, rotatably attached at a second end to the second compression member, and rotatably attached between the first and second ends to the body.
In yet another aspect, the swing mount is configured to be detachable from the body via a quick-release pin so as to allow the second compression member to rotate freely about the second end of the lever arm.
In still another aspect, the first compression member further includes a first leg and a first compression foot, wherein the first leg is attached at one end to the body and extends inwards, towards the second compression member, to attach at the other end to the first compression foot. Further, the second compression member includes a second leg and a second compression foot, wherein the second leg is attached at one end to the body and extends inwards, towards the first compression member, to attach at the other end to the second compression foot. Preferably, the first compression foot is parallel to the second compression foot across the gap defined therebetween and each compression foot is rotatable about a long axis of its respective leg.
The present invention has several advantages. The clamp reduces the incidence of interlaminate burring by tightly clamping together the parts being drilled. In addition, the clamp is powered, which reduces operator fatigue. In particular, the air pressure cylinder acts quickly and provides sufficiently high clamping forces to reduce burring. The drill bit assembly guide ensures that the holes are drilled in the area of pressure application and also ensures accurate positioning and orientation of the holes. The use of air pressure cylinders to actuate both of the compression members allows maximum clearance for positioning of the clamp over large parts. The elongated foot shape of the compression members avoids damage to the parts from high pressure areas, as well as distributes the pressure over a large area for drilling multiple holes without repositioning the clamp. The release pin of the swing mount allows the second compression member to be rotated open for additional clearance to position the clamp over large parts. The lever arm of the linkage increases the force applied by the pressure cylinder to the second compression foot.